The invention concerns a catalytic process for the preparation of halogenated 2,2-bis(trifluoromethyl)-1,3-dioxolanes.
2,2-Bis(trifluoromethyl)-1,3-dioxolane is a known compound which may be halogenated according to a number of known methods to produce various halo-isomers at the 4,5 or 4 and 5 positions. For example, U.S. Pat. No. 2,925,424 describes a batch photochemical chlorination of 2,2-bis(trifluoromethyl)-1,3-dioxolane. The reaction was conducted at 50.degree. C. for 2.5 hours. A 68% yield of 2,2-bis(trifluoromethyl)-4,4,5,5-tetrachloro-1,3-dioxolane was obtained upon fractionation of crude product. See Example 9.
U.S. Pat. No. 4,535,175 discloses a batch photochemical chlorination of 2,2-bis(trifluoromethyl)-1,3-dioxolane to yield a mixture of di-, tri- and tetra-chloro derivatives. The reaction proceeds rather slowly. Example 1 of the patent details the production of 2,2-bis(trifluoromethyl)-4,4,5-trichloro-5-fluoro-1,3-dioxolane by reacting 2,2-bis(trifluoromethyl)-4,4,5,5,-tetrachloro-1,3-dioxolane, HF and antimony chloride at 70.degree. C. for 5 hours.
U.S. Pat. No. 3,794,791 discloses a batch photochlorination of 2,2-bis(trifluoromethyl)-1,3-dioxolane at -15.degree. C. Example 1 describes the synthesis of 2,2-bis(trifluoromethyl)-4-chloro-1,3-dioxolane. Example 2 of the patent describes the synthesis of 2,2-bis(trifluoromethyl)-4,5-dichloro-1,3-dioxolane.
G.B. 1,361,346 discloses the preparation of 2,2-bis(trifluoromethyl)-4,5-dichloro-4,5-difluoro-1,3-dioxolane by fluorinating 2,2-bis(trifluoromethyl)-4,4,5, 5,-tetrachloro-1,3-dioxolane with SbF.sub.3 /SbCl.sub.5 at 120.degree. C.